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| United States Patent |
5,226,945
|
|
Frisch
|
July 13, 1993
|
Aqueous herbicidal dispersion concentrate containing linuron and
monolinuron as active substances
Abstract
Aqueous herbicidal dispersion concentrate containing linuron and
monolinuron as active substances
Storage-stable, aqueous herbicidal dispersion concentrate containing
(a) linuron and monolinuron as active substances and
(b) an alkali metal salt of a sulfosuccinic monoester as dispersant,
prepared by reacting a polyglycol ether of a condensation product of a
(C.sub.8 -C.sub.12)-alkylphenol and formaldehyde with maleic anhydride and
an alkali metal sulfite,
the dispersion concentrate having a pH from 2.5 to 7.5.
| Inventors:
|
Frisch; Gerhard (Wehrheim, DE)
|
| Assignee:
|
Hoechst Aktiengesellschaft (Frankfurt am Main, DE)
|
| Appl. No.:
|
778393 |
| Filed:
|
October 16, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
504/148; 504/364 |
| Intern'l Class: |
A01N 047/30 |
| Field of Search: |
71/120,DIG. 1
|
References Cited
U.S. Patent Documents
| 3888828 | Jun., 1975 | Grossmann | 71/93.
|
| 4594096 | Jun., 1986 | Albrecht et al. | 71/93.
|
| 4804399 | Feb., 1989 | Albrecht et al. | 71/93.
|
| Foreign Patent Documents |
| 562459 | May., 1984 | AU.
| |
| 0110174 | Jun., 1984 | EP.
| |
| 0297305 | Jan., 1989 | EP.
| |
| 2132405 | Jan., 1973 | DE.
| |
| 2144415 | Feb., 1973 | FR.
| |
Other References
The Agrochemicals Handbook, "Linuron" pA248: editors D. Hartley and Hamish
Kidd; Royal Society of Chemistry, England 1987.
|
Primary Examiner: Raymond; Richard L.
Assistant Examiner: Bembenick; B.
Attorney, Agent or Firm: Curtis, Morris & Safford
Claims
I claim:
1. An aqueous herbicidal dispersion concentrate containing
a) linuron and monolinuron as active substances, and
b) an alkali metal salt of a sulfosuccinic monoester as dispersant,
prepared by reacting a polyglycol ether of a condensation product of a
(C.sub.8 to C.sub.12)-alkylphenol and formaldehyde with maleic anhydride,
having a pH from 2.5 to 7.5.
2. The dispersion concentrate as claimed in claim 1, which contains
furthermore
(c) a cosurfactant selected from the group comprising lignosulfonates,
alkali metal salts of a sulfonic acid of an aromatic condensation product,
and alkali metal salts of a sulfonic acid of a polymeric aromatic
substance.
3. The dispersion concentrate as claimed in claim 2, which contains 0.1 to
8% by weight, of component (c).
4. The dispersion concentrate as claimed in claim 1, in which the ratio by
weight of linuron to monolinuron is 10:1 to 1:10.
5. The dispersion concentrate as claimed in claim 1, which contains linuron
and monolinuron in each case in an amount of from approximately 8 to
approximately 35% by weight.
6. The dispersion concentrate as claimed in claim 1, which contains 0.1 to
20% by weight, of component (b).
7. The dispersion concentrate as claimed in claim 1, which contains a
buffer system based on citric acid and ammonium and/or alkaline earth
metal salts thereof and dihydrogen phosphates as agents for adjusting the
pH.
8. The dispersion concentrate as claimed in claim 1, which additionally
contains thickeners, antifreeze agents, defoamers and/or preservatives.
9. The dispersion concentrate as claimed in claim 1, which has a pH of 3.5
to 7.0.
10. The dispersion concentrate as claimed in claim 1, which has a pH of
3.0.
11. The dispersion concentrate as claimed in claim 2, which contains 1 to
5% by weight, of component (c).
12. The dispersion concentrate as claimed in claim 1, in which the ratio by
weight of linuron to monolinuron is approximately 1:1.
13. The dispersion concentrate as claimed in claim 1, which contains
linuron and monolinuron in each case in an amount of from approximately 7
to 23% by weight.
14. The dispersion concentrate as claimed in claim 1, which contains 2 to
16% by weight, of component (b).
Description
The present invention relates to an aqueous herbicidal dispersion
concentrate containing linuron and monolinuron as active substances.
To date, it is known that the herbicides linuron
[3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea] and monolinuron
[3-(4-chlorophenyl)-1-methoxy-1-methylurea] exist as mixed formulations in
the form of wettable powders and formulations in the form of emulsion
concentrates (commercial product Afalon S.RTM., manufactured by HOECHST
AG).
However, expensive grinding and filtering plants are required in the
preparation of wettable powder formulations, and also frequently expensive
carriers. Wettable powders also have the disadvantage that they product
dust during handling. They can only be dosed with difficulty. The user can
easily become contaminated by such formulations which produce dust, and
suffer damage. Furthermore, spray mixtures prepared from wettable powders
tend to be inhomogeneous; the active substance particles and solids
particles settle relatively rapidly.
In particular, the emulsion concentrates of the two abovementioned active
substances have the disadvantage that it is only possible to achieve a low
active substance content of 90:90 g/l.
Since aqueous dispersions do not have the disadvantages of the wettable
powders and, in principle, allow higher active substance contents because
linuron and monolinuron are insoluble in water, and because they can also
be prepared with a relatively low outlay in terms of equipment, attempts
have been made to prepare aqueous dispersions of both active substances
with a markedly higher active substance content than, for example, the
emulsion concentrates; however, such attempts have failed to date, namely
because of crystal growth owing to the relatively good solubility of the
two active substances in water, because of grinding problems, etc.. Such
attempts gave dispersions of low stability which showed substantial
flocculation, sedimentation or even solidification. Even the use of
coloring matter for preventing crystallization did not result in the
desired aim of providing an aqueous dispersion of linuron with monolinuron
which shows long-term stability (2 years at room temperature or 3 months
at 50.degree. C.), does not show crystal growth, which puts stability at
risk, and which does not flocculate, sediment or even solidify.
Emulsifiable concentrates and wettable powders exist in the form of
one-phase systems; in contrast, aqueous dispersion concentrates of solid
active substances represent two-phase systems (solid/liquid), which, in
general, are instable and their mixture tends to separate, this tendency
increasing with increasing storage time and temperature. Practical
requirements demand that dispersion concentrates must be storage-stable
over two years; they must furthermore remain pourable. The solidification
of dispersions and/or the formation of irreversible sediments must be
excluded.
Even though there exist theoretical considerations as to the conditions for
establishing stable suspensions, it is impossible to predict optimum
formulation additives directly because of the large number of criteria to
be taken into account. In practice, it is usually insufficient, for
example, to investigate the suspension behavior of an individual
production batch since minute changes in amounts of secondary components
in the individual active substance batches can decisively impair the
stability of the dispersions.
Optimum formulation of herbicidal ureas, for example linuron, using
partially hydrolyzed polyvinyl acetates, as described in U.S. Pat. No.
4,071,617, has therefore proved to be impossible since viscous sediments
which are not redispersible are formed when these formulation additives
are used. If nonionic emulsifiers, vegetable gums and anionic
surface-active agents, for example in accordance with U.S. Pat. No.
3,948,636 or British Patent Specification 148,010, are employed, the same
effect becomes apparent.
EP 0,110,174 discloses liquid pesticidal compositions in the form of
aqueous suspension concentrates which contain, besides the active
substance, the following essential components:
(1) an alkali metal salt of a sulfosuccinic monoester, prepared by reacting
a polyglycol ether of a condensation product of (C.sub.8 - to
C.sub.12)-alkylphenol and formaldehyde with maleic anhydride and an alkali
metal sulfite,
(2) an alkali metal salt of a lignosulfonic acid and
(3) a swellable alkaline earth metal silicate, components (2) and (3) being
present in the mixture in equal parts.
This European Patent specifically emphasizes the complete loss of the
advantageous properties, i.e. in particular the storage stability and
pourability, of the suspension concentrate when only one component of the
three essential formulation ingredients sulfosuccinic monoester, salt of
lignosulfonic acid and swellable alkaline earth metal silicate is absent,
which has also been demonstrated by comparison tests. From amongst a large
number of pesticides, linuron and monolinuron are, inter alia, generally
mentioned as herbicidal active substances which can be employed. No
mention is made in this publication of the essential importance of the pH
of the suspension concentrate.
Surprisingly, it has now been found that storage-stable aqueous herbicidal
dispersion concentrates having a considerably higher active substance
content of linuron and monolinuron compared with the emulsion concentrates
known to date can be obtained when the dispersing agent used is an alkali
metal salt of a sulfosuccinic monoester, prepared by reacting a polyglycol
ether of a condensation product of a (C.sub.8 - to C.sub.12)-alkylphenol
and formaldehyde with maleic anhydride and an alkali metal sulfite, and
the pH of the concentrate is adjusted to 2.5, preferably 3.0, to 7.5.
The present invention therefore relates to an aqueous herbicidal dispersion
concentrate containing
a) linuron and monolinuron as active substances, and
b) an alkali metal salt of a sulfosuccinic monoester as dispersant,
prepared by reacting a polyglycol ether of a condensation product of a
(C.sub.8 -C.sub.12)-alkylphenol and formaldehyde with maleic anhydride and
an alkali metal sulfite, having a pH from 2.5, preferably 3.0, to 7.5.
The dispersion concentrate preferably furthermore contains a cosurfactant
selected from the group comprising lignosulfonates, alkali metal salts of
a sulfonic acid of an aromatic condensation product, and alkali metal
salts of a sulfonic acid of a polymeric aromatic substance, this
cosurfactant mainly acting as an improver of the dispersing and grinding
properties.
As shown by comparison tests below, both the abovementioned specific
dispersant and the specific pH range are critical.
The alkali metal salt of a sulfosuccinic monoester, in particular the
sodium salt, which is employed in the dispersion concentrate according to
the invention can be prepared analogously to German Patent Specification
2,132,405, where, in particular, monooctylphenols or monononylphenols are
employed and where the molar ratio of alkylphenol to formaldehyde varies
within the range from 2:1 to 10:9. The polyglycol ether of this
condensation product of alkylphenol and formaldehyde preferably contains 2
to 8 mol of alkylene oxide units, in particular ethylene oxide units, per
mol of alkylphenol. The alkali metal sulfite used is preferably sodium
sulfite.
A sulfosuccinic monoester prepared from 3 mol of nonylphenol, 18 mol of
ethylene oxide, 2 mol of formaldehyde, 3 mol of sodium sulfite and 3 mol
of maleic anhydride is preferred; it can be employed in the form of a dry
powder or in the form of an aqueous solution (in general 35% strength).
The dispersion concentrate according to the invention contains the alkali
metal salt of the sulfosuccinic monoester in an amount of from
approximately 0.1 to approximately 20% by weight, preferably 2-16% by
weight.
The dispersion concentrate can contain linuron and monolinuron each in an
amount of from approximately 8 to approximately 35, preferably 7 to 23% by
weight; accordingly, the active substance content which is possible is
considerably higher than that of the known emulsion concentrates.
The ratio by weight of the active substances linuron:monolinuron is
approximately 10:1 to 1:10, in particular approximately 1:1.
As mentioned above, the dispersion concentrate according to the invention
preferably contains a specific cosurfactant; such surface-active compounds
are commercially available, mention being made of the products mentioned
in the notes to Tables I and II below. If at all, the dispersion
concentrate according to the invention contains the cosurfactant in an
amount of from 0.1 to 8% by weight, preferably 1 to 5% by weight.
The pH of the dispersion concentrate is essential for the stability of the
latter. It is advantageously below approximately 7.5 and above 2.5, better
approximately 3. The pH is preferably 3.5 to 7.0. If the abovementioned
broad pH range is not adhered to, the dispersion concentrate tends to
become instable within a short time.
The pH can be adjusted using buffer systems, advantageously citric acid
including the ammonium and alkaline earth metal salts thereof, or
dihydrogen phosphates, for example KH.sub.2 PO.sub.4.
The dispersion concentrates according to the invention can additionally
contain conventional formulation auxiliaries such as freezing-point
depressants for increasing stability to frost, thickeners for improving
the viscosity, and preservatives and/or defoamers.
Examples of freezing-point depressants are, inter alia, ethylene glycol,
propylene glycol, glycerol, urea and the like.
Viscosity improvers which can be employed are customary inorganic or
organic thickeners; examples of the latter are those based on
polysaccharides (for example the commercial products Rhodopol 23.RTM.
supplied by Rhone Poulenc and Kelzan.RTM. supplied by Kelco Corp.), based
on polyvinyl alcohols (commercial product Mowiol.RTM. supplied by HOECHST
AG), or based on methylcellulose (for example the commercial product
Tylose.RTM. supplied by HOECHST AG).
Examples of preservatives are benzoic acid, sorbic acid, formaldehyde and
traces of fungicidal active substances (for example the commercial
products Bronidox L.RTM. supplied by Henkel KGaA, Kobate C.RTM. supplied
by Rhone Poulenc, Mergal KM 200.RTM. supplied by Riedel-de Haen).
Finally, examples of defoamers are those based on silicone (commercial
products Silcolapse.RTM. supplied by Rhone Poulenc, and the antifoam range
supplied by Wacker Chemie GmbH, for example the defoamer SE 2).
To prepare the dispersion concentrates according to the invention, the
components are stirred with water, then, if appropriate, the resulting
coarse suspension is comminuted by grinding on a corundum mill or a
toothed-disk mill to a fineness of approximately 200 microns, and the
product is subsequently ground in ball mills or sand mills until the
particles of the dispersion exist in particle sizes from 0.1 to 10
microns, preferably below 5 microns. The particle sizes are determined by
means of a disk centrifuge or a Coulter counter.
The dispersion concentrate according to the invention is applied in a
simple manner by diluting the dispersion concentrates with the desired
amount of water, stirring the mixture briefly and applying it to the
plant. Compared with spray mixtures prepared from wettable powders or
emulsifiable concentrates, the spray mixtures obtained from the dispersion
concentrates according to the invention are distinguished, in particular,
by a uniform distribution of the active substances which is retained even
after a standing period of 24 hours. In contrast, suspensions of wettable
powders undergo rapid separation; often, half of the active substance has
settled after a standing time of half an hour. In contrast, emulsions have
the disadvantage that they can only be prepared with a low content of the
active substances linuron and monolinuron, as has already been mentioned
above.
The examples which follow are intended to illustrate the invention in
greater detail.
EXAMPLES 1 to 20
Aqueous suspension concentrates containing linuron and monolinuron as
active substances were prepared from the components mentioned in each case
in Table I below by grinding the constituents in a ball mill using glass
spheres of diameter 2 mm.
The dispersions were ground to such a fineness that 90% by weight of the
suspended particles had a diameter of less than 5 microns and 30 to 40% by
weight of the particles a diameter of less than 1 micron, the particle
sizes being measured by means of a disk centrifuge.
At a storage time of 3 months at 50.degree. C., the compositions according
to the invention mentioned in Table I proved to be stable and satisfactory
as regards their application properties.
COMPARISON EXAMPLES 1 to 7
In contrast, the compositions mentioned in Table II show flocculation and
extensive sedimentation, in some cases even solidification. This is caused
by the fact that they did not contain the dispersant alkali metal salt of
a sulfosuccinic monoester according to the invention and/or had a pH above
7.5 (upper limit according to the invention).
TABLE I
__________________________________________________________________________
Examples 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
__________________________________________________________________________
Linuron 8.7
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
Monolinuron
8.7
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
Defoamer.sup.1)
2.0
2.0
2.0
2.0 2.0
2.0
2.0
2.0
2.0 2.0
2.0
Defoamer.sup.2)
1.0 1.0
1.0
1.0 1.0
1.5
Glycerol 8.0 8.0
Propylene glycol
8.0
8.0
8.0
8.0
8.0 8.0
8.0
8.0
8.0
8.0 8.0
8.0 8.0
Urea 6.0 6.0
Dispersant.sup.3)
16.0
4.0
4.0
4.0
4.0 5.0
4.0
4.0
5.0
6.0 4.0
4.0
5.0
4.0
4.0 4.0
4.0
Cosurfactant.sup.4)
2.0
Cosurfactant.sup.5)
0.5 2.0 2.0
2.0 2.0
2.0 2.0
2.0 2.0
Cosurfactant.sup.6)
2.0
2.0
2.0 2.0 2.0
Cosurfactant.sup.7) 2.0 2.0
Cosurfactant.sup.8) 2.0
Thickener.sup.9)
0.2
0.5
0.2 0.2 0.15
0.15 0.15
0.25
0.2
0.2
0.2
0.2
0.2 0.2
0.2
Thickener.sup.10) 0.2
Thickener.sup.11) 1.0
2.0 2.0
2.0
2.0
2.0 2.0
2.0
1.0
2.0
2.0 2.0
1.0
Thickener.sup.12)
1.0 1.0
Citric acid
0.4
0.2
0.2
0.2 0.6 0.2
0.2
0.6 0.4
0.4
0.4
0.6
3.0 0.4
KH.sub.2 PO.sub.4 1.0 1.0 3.0
Water to 100%
pH 4.4
5.9
7.1
7.0
6.3 5.0
6.5
7.0
7.3
4.8 4.1
4.4
5.6
4.2
2.9 5.6
6.0
__________________________________________________________________________
TABLE II
______________________________________
Comparison
Examples 1 2 3 4 5 6 7
______________________________________
Linuron 17.3 17.3 17.3 17.3 17.3 17.3 17.3
Monolinuron
17.3 17.3 17.3 17.3 17.3 17.3 17.3
Defoamer.sup.1)
2.0 2.0 2.0 2.0 2.0 2.0
Defoamer.sup.2) 1.0
Glycerol 8.0
Propylene glycol
8.0 8.0 8.0 8.0 8.0 8.0
Dispersant.sup.3) 4.0 5.0 4.0 4.0
Dispersant.sup.13)
2.0
Cosurfactant.sup.6)
2.0 2.0 2.0 2.0 2.0
Cosurfactant.sup.7) 2.0
Cosurfactant.sup.5) 2.0
Thickener.sup.9) 0.15 0.25 0.2
Thickener.sup.10) 0.2
Thickener.sup.11)
1.0 1.0 2.0 1.0 2.0 1.0 1.0
Thickener.sup.12)
1.0 1.0 1.0
Citric acid
0.2 0.2
K citrate 0.2
KH.sub.2 PO.sub.4 2.0 1.0
Water to 100%
pH 7.0 8.4 9.1 >0.0 8.5 7.0 6.5
______________________________________
Notes to Tables I and II
.sup.1) Defoamer based on silicone, commercial product SE 2 supplied by
WackerChemie GmbH;
.sup.2) Defoamer based on silicone, commercial product Silicolapse .RTM.
5020 supplied by Rhone Poulenc;
.sup.3) Condensation product of 3 mol of nonylphenol and 2 mol of
formaldehyde, oxethylated with 18 mol of ethylene oxide, reacted with 3
mol of maleic anhydride and 3 mol of sodium sulfite, in the form of a 35%
strength aqueous solution;
.sup.4) Commercial product Galoryl .RTM. DT 12 supplied by CFPI, 92233
Gennevilliers, France; (sodium sulfonate of an aromatic polymer);
.sup.5) Commercial product Galoryl .RTM. DT201 supplied by CFPI;
(condensed sulfonic acids in the form of the sodium salts);
.sup.6) Commercial product Vanisperse .RTM. CB supplied by Borregaard
Industries Ltd., Sarpsborg, Norway; a lignosulfonate with 0.17 sulfonyl
groups per phenylpropane unit, a total sulfur content of 2.4% and a pH of
8.8 (3% strength solution);
.sup.7) Commercial product Vanisperse .RTM.A supplied by Borregaard; a
lignosulfonate with 0.17 sulfonyl groups per phenylpropane unit, a total
sulfur content of 2.4% and a pH of 7.3 (3% strength solution);
.sup.8) Commercial product Ligninsulfonat 300.36 .RTM. (Lignosol FTA)
supplied by Hansatronic;
.sup.9) Commercial product Rhodopol .RTM.23 supplied by Rhone Poulenc; a
thickener based on polysaccharides;
.sup.10) Commercial product Kelzan supplied by Kelco Corp., USA; a
thickener based on polysaccharides;
.sup.11) Thickener based on a mineral alumosilicate;
.sup.12) Thickener based on colloidal Hg/Al silicate; commercial product
Veegum .RTM. supplied by Vanderbilt.
.sup.13) Anionic condensation product based on
cresols/formaldehyde/nonylphenol/sodium sulfite (HOES 1694)
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